FINE-STRUCTURE OF THE 1S5F AND 1S5G LEVELS OF HE-I

The fine structure of the 1 s 5f and 1 s 5g levels of He I was measured using microwave spectroscopy. The helium atoms were excited by ion impact, and the eleven allowed 1 s 5f2S+1F(J)-1 s 5 g 2S'+1G(J), transitions near v almost-equal-to 15 GHz were induced and detected by measuring the 1 s 4d - 1 s 2 p or 1 s 3d - 1 s 2 p spectral-line intensities of the impact radiation as a function of the microwave frequency. The measured transition frequencies are in accord with theoretical values and, except for one transition frequency, with earlier experimental data. The existing discrepancy between these earlier data and theory could be solved.